The present invention relates to a toner cartridge for supplying toner accommodated in the toner cartridge attached to a toner supply section of an image forming apparatus.
Performance of office automation apparatus such as a printer and copier has been enhanced recently. In this trend of the times, reduction of the size and cost of the apparatus is demanded. Therefore, it is required to reduce the size and cost of an expensive, large and complicated color image forming apparatus. After the color image forming apparatus has been downsized, it tends to be applied for personal use.
Concerning the quality of printing, there is a demand for an electrophotographic printing system that is more advantageous than other systems such as a dot-impact, thermal-transfer and ink-jet system.
Therefore, it is necessary to develop and offer a small handy color image forming apparatus of electrophotography, the cost of which is low, and the performance of which is high.
Compared with a monochromatic image forming apparatus, it is difficult to downsize a color image forming apparatus because a plurality of developing units of different colors are provided in the color image forming apparatus. In the case of a common color image forming apparatus having 4 developing units of Y (yellow), M (magenta), C (cyan) and K (black), the apparatus is downsized by using small developing units and a small photoreceptor for image formation. However, when each developing unit arranged around the photoreceptor is downsized, an amount of toner accommodated in the developing unit is reduced, which causes a problem. In other words, it is impossible to downsize the apparatus having a toner accommodating section in the developing unit. In order to solve the above problem, the toner accommodating section for supplying toner is arranged outside of the developing unit. Since a plurality of toner supply sections must be arranged in a color image forming apparatus, it is necessary to reduce the dimensions of the toner supply sections for accomplishing the object of downsizing.
Conventionally, there are provided 2 types of toner supply sections. One is a type in which a toner hopper for accommodating toner is arranged in the image forming apparatus and only toner is supplied from a toner container to the hopper, that is, a toner cartridge is not arranged in the image forming apparatus. The other is a type in which a toner cartridge is arranged in the image forming apparatus so that toner is supplied to the developing unit from the toner cartridge. When importance is attached to maneuverability of the apparatus, the cartridge type is more effective than the type in which toner is manually supplied without using the cartridge.
For this reason, the type in which the toner cartridge is arranged in the image forming apparatus is employed. A conventional image forming apparatus having a toner cartridge will be explained here.
There are provided 4 types of toner cartridges as described below.
(1) A cylindrical toner cartridge is attached in parallel with a rotational center of the developing sleeve of the developing unit while an opening portion of the toner cartridge is located upward. Then the toner cartridge is rotated by a half revolution so that toner can be supplied into the cartridge.
(2) A bottle-shaped toner cartridge is connected with a toner supply section while an opening portion of the toner cartridge is located upward. Then the bottle is rotated by a half revolution so that toner can be supplied into the bottle.
(3) A cylindrical toner cartridge is held horizontally, on the inner circumferential surface of which spiral protrusions are provided. Then the toner cartridge is rotated, and toner accommodated in the cartridge is conveyed to an end of the cartridge. The conveyed toner is discharged from an opening formed at the end to the toner supply section.
(4) Type (4) is a variation of type (3). In the type (4), a screw for conveying toner is arranged in the toner cartridge.
When importance is attached to the maneuverability of the apparatus, the types (1) and (2) have the following disadvantages:
In the types (1) and (2), toner is supplied into the cartridge when the cartridge is attached. Therefore, the toner cartridge must be shaken before the cartridge is attached so that the accommodated toner can be fluidized. PA1 Toner conveyed to an end surface of the toner cartridge is discharged from the end surface portion (the end surface or the circumferential surface of the end). However, the toner hopper or developing unit to which the toner is supplied is located at a position lower than the discharging section. Examples in which the opening is located at the circumferential surface are disclosed in Japanese Patent Publication Open to Public Inspection Nos. 1681/1992, 477/1992 and 2881/1991. In all examples described above, a portion for receiving toner discharged from the cartridge is located at a position lower than the cartridge. A conveyance section for conveying the toner to the next unit (for example, the developing unit) is illustrated in the drawing of each example. However, since the device functions as a toner supply unit, it is necessary to arrange the device at a higher position. Under the toner cartridge, a wide dead space is generated at a position where the toner conveyance unit is not arranged. Due to the foregoing, it is difficult to downsize the image forming apparatus. PA1 (1) One is a clam-shell type image forming apparatus. PA1 (2) The other is an image forming apparatus in which a process unit integrally having a photoreceptor, developing units and cleaning unit can be removed from the main body of the image forming apparatus. PA1 The toner cartridge includes a cylindrical container for accommodating toner having an opening for discharging toner accommodated in the container and also having spiral protrusions on the inner circumferential surface. The toner cartridge is arranged in the image forming apparatus approximately horizontally, and toner is conveyed and discharged when the container is rotated. A scooping section is attached to the opening of the container, and toner can be discharged from the container by the scooping section at an upper portion of the rotational axis of the toner cartridge.
In order to prevent the accommodated toner from clogging in the cartridge, countermeasures must be taken, so that the structure becomes complicated and the dimensions are extended. As a result, the cost is increased.
From the viewpoint of structure, it is obvious that the type (4) is more expensive than the type (3).
Due to the foregoing, the toner cartridge of type (3), on the inner circumferential surface of which spiral protrusions are provided, is advantageous since its maneuverability is high.
According to the prior art, the apparatus can not be sufficiently downsized from the following reasons:
Next, examples will be explained, in which toner is discharged from the end surface of the toner cartridge. The examples are disclosed in Japanese Patent Publication Open to Public Inspection No. 266380/1990 and Japanese Patent Publication Nos. 6194/1993 and 60387/1988. In the above examples, the opening portion of the toner cartridge functions to discharge toner at a position lower than the rotational shaft of the cartridge. That is, the discharged toner must be received by the receiving section located at a position lower than the opening section. Accordingly, the toner receiving section is located at a position lower than the lowermost surface of the toner cartridge. From the viewpoint of downsizing, the above examples are the same as the example in which the opening section is provided in the periphery of the toner cartridge. Therefore, the above examples are disadvantageous in downsizing. The above examples are disadvantageous in that the dead space is generated under the toner cartridge, so that the height of the device is increased.
Due to the foregoing, even in the apparatus in which the toner cartridge having spiral protrusions on the inner circumferential surface is used, a dead space is generated and the dimensions of the apparatus are extended.
The above problems are solved by the present invention. The first object of the present invention is to provide a toner cartridge by which a compact and handy toner supply section can be realized at low cost when a toner discharge section of the toner cartridge is located at a position higher than a rotational center of the toner cartridge, and a toner receiving section (toner hopper) for receiving toner discharged from an opening section is located on the substantially same surface as the toner cartridge.
In order to reduce the width and length of an image forming apparatus, it is necessary to the external dimensions of a sheet conveyance passage for conveying sheets. In the conventional example in which a plurality of toner supply sections are provided, the toner supply sections are arranged outside of the sheet conveyance passages. Accordingly, the width of the apparatus becomes equal to the total of the width of the sheet conveyance passage and the width of the toner supply section. In other words, the width of the apparatus is excessively increased. In order to improve the maneuverability, especially in order to improve the performance of jam clearance, there are provided two types of image forming apparatus.
In order to reduce the dimensions of the color image forming apparatus at a low cost, type (2) is more effective than type (1). Type (2) is primarily applied to a monochromatic page printer, and the toner supply section is not individually provided but integrated with each developing unit. Therefore, technique of type (2) can not be applied to the image forming apparatus, that is, according to the prior art, it is impossible to reduce the dimensions of the apparatus and improve the maneuverability at the same time. In order to develop an inexpensive small color image forming apparatus, it is necessary to effectively arrange a plurality of toner supply sections in a sheet conveyance passage. It is also necessary to improve the maneuverability of the apparatus in the cases of jam clearance and maintenance of the apparatus.
The above problems are solved by the present invention. The second object of the present invention is to provide a color image forming apparatus characterized in that: the dimensions of a toner supply section are reduced; and the toner supply section is effectively arranged so as to downsize the apparatus. In this way, in the cases of toner supply, jam clearance and maintenance, the apparatus can be easily and simply handled.